Experimental and theoretical study of the products from the spontaneous dimerization of DL- and D-glyceraldehyde

The predominant molecular structure of DL and D-glyceraldehyde has been studied with infrared and nuclear magnetic resonance spectroscopies. Both techniques show that these compounds at room temperature have a minor percentage of the aldehydic form. These studies showed that D-(+)-glyceraldehyde coexists in a minor proportion as a component of a complex mixture of diasteroisomers of the 2,5-dihydroxy-3,6-dihydroxymethyl-1,4-dioxane, while the racemic mixture is made of two main compounds. The stability of the isolated diasteroisomers is controlled by the formation of intramolecular hydrogen bonds that are formed under the control of the anomeric effect which defines the favored position for the hydroxyl group. The endo and exo-anomeric interactions have their origin in the stereoelectronic interaction nO ® s*C-O. Using theoretical calculations at B3LYP/6-31G(d,p) level, it was possible to establish the structure of the favored conformers.